Investigator: R. Lane Smith, PhD Project Staff: Thomas P. Andriacchi, PhD; David J. Schurman, MD; and Stuart B. Goodman, MD, PhD Project Category: Arthritis - 2000 Background: A number of soluble factors, such as proinflammatory cytokines, growth factors and hormones, are potential mediators of the effects of altered mechanical load on changes in cartilage metabolism and the integrity of the extracellular matrix. The rationale underlying this proposal is that positive and negative effects of these families of soluble effector molecules are either stimulated or inhibited depending on the mechanical loading environment of the joint. Finite element studies of cartilage loading provide a descriptive pattern of the regional mechanical stresses and strains that may influence cartilage metabolism. Thus, completely different mechanical loading conditions such as that represented by application of fluid-induced shear stress (FISS) and intermittent hydrostatic pressure (IHP) would be predicted to significantly influence articular chondrocyte metabolism in different ways. The purpose of this proposal is to define the effects of two distinct types of mechanical load, fluid-induced shear stress and intermittent hydrostatic pressure, on proteoglycan synthesis and matrix metalloproteinase expression in human osteoarthritic articular cartilage cells. Hypothesis: The hypothesis to be tested here is that distinct intracellular signaling pathways underlie the articular cartilage response to intermittent hydrostatic pressure and shear stress. Fundamental knowledge exists regarding the effect of the proinflammatory cytokine, interleukin-1, on the inhibition of cartilage extracellular matrix macromolecule synthesis and induction of cartilage degrading enzyme synthesis by chondrocytes. However, effects of mechanical loads on the reaction of human osteoarthritic articular chondrocytes to the inflammatory cytokine, IL-1beta, remain unclear. Objectives: The specific aims will quantify effects of fluid-induced shear stress and intermittent hydrostatic pressure on human osteoarthritic articular chondrocytes in vitro to: (1) test the hypothesis that IHP and FISS stimulate proteoglycan synthesis in OA chondrocytes; (2) test the hypothesis that IHP and FISS modulate IL-1beta induced inhibition of proteoglycan synthesis; (3) test the hypothesis that IHP and FISS alter endogenous MMP-9 expression in OA chondrocytes; (4) test the hypothesis that IHP and FISS alter IL-1beta induced expression of MMP-9 in OA chondrocytes. Procedures: The expected outcome is that IHP and FISS will function as an effective stimulus for increased matrix synthesis in osteoarthritic chondrocytes. However, the expectation is that FISS and IHP will show dissimilar capacities to overcome the IL-1beta induced shift of chondrocyte metabolism from cartilage maintenance to matrix destruction. The results of this study will be of importance to the fields of orthopaedics, rheumatology and rehabilitation medicine. The techniques will involve analysis of gene expression using Northern blotting, cytokine analysis using ELISA, quantification of proteolytic activity using zymography, Western blotting and peptide fragment analysis. Funding Source: NIH |
